<p>The escalating global burden of cancer, marked by high incidence and mortality, necessitates more effective therapeutic strategies. A major bottleneck in clinical translation is the long-standing reliance on subcutaneous tumor models, which fail to recapitulate the complex physiological and pathological features of human malignancies. These ectopic models lack organ-specific barriers—such as the prostatic capsule, cervicovaginal mucus, and dense desmoplastic stroma—and cannot reproduce authentic metastatic niches or immune heterogeneity. Consequently, this review advocates a paradigm shift toward orthotopic–TME–informed nanomedicine design. We systematically evaluate recent progress in nanotherapeutics across twelve major malignancies, categorized into three strategic domains: (i) barrier-penetrating platforms engineered to navigate organ-specific physical and biochemical constraints; (ii) metastasis-targeted delivery systems that exploit native lymphovascular pathways; and (iii) microenvironment-responsive mechanisms that adapt to localized stimuli such as hypoxia and acidity. By integrating data from a wide range of studies, we highlight how orthotopic models provide a more rigorous platform for assessing drug penetration and therapeutic efficacy than conventional subcutaneous models. Furthermore, we critically discuss existing challenges, including manufacturing scalability, the bio–nano interface, and long-term toxicological safety. Looking forward, we propose a strategic roadmap that emphasizes the use of patient-derived orthotopic xenografts (PDOX), multi-omics data integration, and the development of closed-loop adaptive nanosystems. By aligning nanomaterial properties with constraints inherent to the orthotopic microenvironment, this review aims to provide a blueprint for the next generation of precision oncology platforms that can successfully bridge the gap from bench to bedside.</p> Graphical Abstract <p></p>